title: Human casein alpha s1 (CSN1S1) skews in vitro differentiation of monocytes towards macrophages.
abstract: BACKGROUND
  The milk-derived protein human Casein alpha s1 (CSN1S1) has recently been detected in blood cells and was shown to possess proinflammatory properties. In the present study, we investigated the effect of CSN1S1 on the differentiation of monocytes.
  
  
  METHODS
  Primary human monocytes were stimulated with recombinant CSN1S1 and compared to cells stimulated with GM-CSF/IL-4 or M-CSF/IFNγ. Morphological changes were assessed by microscopy and quantification of surface markers of differentiation by FACS analysis. Phagocytic activity of CSN1S1 stimulated cells was measured by quantification of zymosan labeled particle uptake. The role of mitogen activated protein kinases for CSN1S1-induced differentiation of monocytes and proinflammatory cytokine expression was assessed by supplementation of specific inhibitors.
  
  
  RESULTS
  CSN1S1 at a concentration of 10 μg/ml resulted in morphological changes (irregular shape, pseudopodia) and aggregation of cells, comparable to changes observed in M-CSF/IFNγ differentiated macrophages. Surface marker expression was altered after 24 h with an upregulation of CD14 (mean 2.5 fold) and CD64 (1.9 fold) in CSN1S1 stimulated cells. CSN1S1 treated cells showed a characteristic surface marker pattern for macrophages after 120 h of incubation (CD14high, CD64high, CD83low, CD1alow) comparable to changes observed in M-CSF/IFNγ treated monocytes. Furthermore, phagocytic activity was increased 1.4 and 1.9 fold following stimulation with 10 μg/ml CSN1S1 after 24 and 48 h, respectively. Early GM-CSF, but not GM-CSF/IL-4 induced differentiation of monocytes towards dendritic cells (DC) was inhibited by addition of CSN1S1. Finally, CSN1S1 induced upregulation of CD14 was impeded by inhibition of ERK1/2, while inhibition of the mitogen activated protein kinases JNK and p38 did not influence cellular differentiation. However, JNK and p38 inhibitors impeded CSN1S1 induced secretion of the proinflammatory cytokines IL-1b or IL-6.
  
  
  CONCLUSIONS
  CSN1S1 skews in vitro differentiation of monocytes towards a macrophage-like phenotype. Data is accumulating that functions of CSN1S1 are beyond nutritional properties and include immunomodulatory effects.
authors.affiliation: Heinrich-Heine-University Düsseldorf, Department of Rheumatology, Moorenstr, 5, 40225 Düsseldorf, Germany. stefan.vordenbaeumen@med.uni-duesseldorf.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Vordenbäumen
authors.forename: Achim
authors.initials: A
authors.lastname: Braukmann
authors.forename: Irina
authors.initials: I
authors.lastname: Altendorfer
authors.forename: Ellen
authors.initials: E
authors.lastname: Bleck
authors.forename: Joachim
authors.initials: J
authors.lastname: Jose
authors.forename: Matthias
authors.initials: M
authors.lastname: Schneider
mesh_terms: D015153:Blotting, Western; D002364:Caseins / Q000235:genetics / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism; D015847:Interleukin-4 / Q000494:pharmacology; D015850:Interleukin-6 / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010587:Phagocytosis / Q000187:drug effects; D017452:Receptors, IgG / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D002364:Caseins; D004791:Enzyme Inhibitors; D053583:Interleukin-1beta; D015850:Interleukin-6; D018950:Lipopolysaccharide Receptors; D017452:Receptors, IgG; D011994:Recombinant Proteins; D015847:Interleukin-4; D016173:Macrophage Colony-Stimulating Factor; D007371:Interferon-gamma; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D020928:Mitogen-Activated Protein Kinases